Ovarian cancer continues to be the most lethal gynecological malignancy with 69% of patients succumbing to their disease. Heterogeneity of ovarian cancer is a formidable challenge, suggesting that targeting multiple biological pathways will almost certainly be required for disease treatment. However, mutations/loss of function in p53 tumor suppressor gene occurs in >96% of all cases of high-grade serous carcinomas (HGSC), the most common form of ovarian cancer. While much work using p53 has focused on its effects as a transcription factor in the nucleus, this proposal will exploit the direct, cell-klling effect that p53 has at the mitochondria. p53's rapid effects at the mitochondria represent the shortest pathway for executing p53 death signaling, which triggers apoptosis. The goal of this proposal is to exploit the p53 intrinsic, direct apoptotic pathway at the mitochondria for use in ovarian cancer therapy. Mitochondrially targeted domains of p53 have never been attempted for ovarian cancer therapy, unlike wild-type p53. We propose to: A) re-engineer a small, monomeric domain of p53 with a mitochondrial targeting signal (MTS) that is highly potent, that kills any cancer cell regardless of p53 status or genetics, and bypasses the dominant negative effect in cancer cells, and B) use a polymeric WSLP delivery system (currently in clinical trials) for effective delivery to cells. Our central hypothesis is that re-engineered, mitochondrially targeted p53 with a proven delivery method administered intraperitoneally will be effective against ovarian cancer. The advantage of using a mitochondrial targeted protein encoded by a gene, rather than a cytotoxic agent [21] is the ability to incorporate a promoter for cancer specific expression of that protein. Ultimately, correction of the p53 pathway and activation of apoptosis may be a universal approach: functional, mitochondrially targeted monomeric p53 re-introduced into cancer cells would act as a sledgehammer, effective under any circumstances (regardless of genetics or the pathway upon which the cancer develops). Three aims are proposed: Aim 1: Design a novel apoptotic gene therapy construct (called DBD-MTS) based on the DBD of p53, coupled to an optimal mitochondrial targeting signal (MTS), driven by a cancer-specific promoter, capable of activating intrinsic apoptosis. Aim 2: Determine the apoptotic potential of DBD-MTS in ovarian cancer cell lines with varying p53 status, individually, and in combo with standard of care, carboplatin and paclitaxel (CPTX). Aim 3: Deliver DBD-MTS using water soluble lipopolymer (WSLP) currently being used in clinical trials by intraperitoneal injection, ino our new syngeneic orthotopic metastatic mouse ovarian cancer model (developed by our collaborator), alone and in combination with carboplatin and paclitaxel (CPTX). If successful, we anticipate this work to advance to a new clinical trial initiated for women diagnosed with late stage (>III) or recurrent high grade serous ovarian cancer and advance the largely unexplored area of mitochondrially targeted p53 gene therapy.